Homer Plessy was a shoemaker from New Orleans. On June 7th 1892 he sat down in a train car reserved for white passengers. The conductor told him to "retire to the coloured car"; Plessy refused and was arrested. He appealed his case to the Supreme Court, arguing that Louisiana's law requiring separate trains for black and white passengers violated the constitution's Reconstruction-era amendments.
The Supreme Court disagreed, ruling in 1896, by a 7-1 vote in Plessy v Ferguson, that Plessy was mistaken in believing that "the enforced separation of the two races stamps the coloured race with the badge of inferiority." The decision entrenched the "Jim Crow" regime of segregation that white Southerners had imposed after Reconstruction. The lone dissenter, Justice John Marshall Harlan, wrote that "our constitution is colour-blind, and neither knows nor tolerates classes among its citizens." It took nearly 60 years for the court to decide that Harlan was right after all.
A computer lets you make more mistakes faster than any other invention, with the possible exceptions of handguns and Tequilla.